## What is classical physics

Classical physics or Newtonian physics is a **discipline that is based on the basic laws of movement on everyday objects**.

Classical physics is known as such, with the publication in 1687 of Newton’s Laws, a mathematical formulation by Isaac Newton (1643-1727) in his work *Philosophiae naturalis principia mathematica*. Newton’s Laws are the basis of physics and classical mechanics.

Classical physics is divided into the following disciplines:

- Kinematics
- classical mechanics
- Hydrostatics and hydrodynamics
- Thermodynamics
- waves and optics
- Electricity and magnetism (later electromagnetism)

## Difference Between Classical Physics and Modern Physics

Modern physics was born in the 20th century with the birth, on the one hand, of Albert Einstein’s General Theory of Relativity published in 1905 and, on the other hand, of quantum mechanics known as the science that studies the behavior of particles. at the atomic and subatomic level.

See also: Modern physics

## Newton’s Laws

Classical physics is based on Newton’s three laws:

### Newton’s First Law or Law of Inertia

Newton’s First Law states that an object will remain at rest or in uniform rectilinear motion (MRU) unless an external force acts on it.

This law only applies to standard problems for objects that have a net internal force of 0. Furthermore, objects are also characterized by the fiction of two forces: the force of circular motion and the force of gravity.

To exemplify Newton’s First Law, let’s imagine a person turning on himself with outstretched arms holding a rope with a ball at the end. The ball will have a circular orbit around the person. If the string breaks, the ball will continue in the straight line where the string left the ball, drawing a uniform rectilinear movement.

See also Uniform Rectilinear Motion.

### Newton’s Second Law or Fundamental Principle of Dynamics

Newton’s Second Law or Fundamental Principle of Dynamics was an advance in the study of movement, since it did not focus only on describing movement but on determining its causes using the following formula:

where F represents the net force on the object, m is the mass of the object, and m is the acceleration. This formula helps to study the results that the same force exerts on objects of different masses.

See also Newton’s Second Law

### Newton’s Third Law or Principle of action-reaction

Newton’s Third Law stipulates that all forces in the Universe occur in pairs, that is, they have a force of equal but opposite magnitude. This indicates the non-existence of isolated forces and constitutes one of the fundamental principles on the symmetry of the Universe.

The Third Law indicates that if there is an external force, such force will be countered by another equal but in the opposite direction. The Law also applies to the internal forces that keep it at rest in this way, since it will not be able to produce a net force on the entire system to set it in motion. Only interaction with another external object will be able to move it.

See also:

- Branches of physics
- Quantum mechanics
- Physical
- Mechanics